Onderzoekingen over de wijze waarop de honingbij haar voedsel verzamelt

Bees were kept in an indoor hive and could reach the outside only through a glass-covered low gallery. In the middle of this was a passage 5 cm. wide, closed by 2 parallel elastic bands. A light push on the elastic was sufficient to restrain her, to mark her or to sample (with a needle) some pollen from her she collected. The species of the pollen was identified. Most bees spent the whole day on one plant species and repeated this several days. Water collectors were marked at the drinking place. They spent the whole day collecting water from one site. By bringing their tongues momentarily into contact with pollen during drinking, these bees suddenly changed their behaviour. They no longer looked for water at the drinking place but for the sweet material they had encountered. They returned to saucers of sugar syrup for days on end. These and complementary observations showed that the environment of the worker bee was extraordinarily limited. Her behaviour was primarily determined by habit

The clinical impact of phase offset errors and different correction methods in cardiovascular magnetic resonance phase contrast imaging: a multi-scanner study

Background: Cardiovascular magnetic resonance (CMR) phase contrast (PC) flow measurements suffer from phase offset errors. Background subtraction based on stationary phantom measurements can most reliably be used to overcome this inaccuracy. Stationary tissue correction is an alternative and does not require additional phantom scanning. The aim of this study was 1) to compare measurements with and without stationary tissue correction to phantom corrected measurements on different GE Healthcare CMR scanners using different software packages and 2) to evaluate the clinical implications of these methods. Methods: CMR PC imaging of both the aortic and pulmonary artery flow was performed in patients on three different 1.5 T CMR scanners (GE Healthcare) using identical scan parameters. Uncorrected, first, second and third order stationary tissue corrected flow measurement were compared to phantom corrected flow measurements, our reference method, using Medis QFlow, Circle cvi42 and MASS software. The optimal (optimized) stationary tissue order was determined per scanner and software program. Velo